An outbreak of type π vaccine-derived poliovirus in Sichuan province, China: emergence and circulation in an under-immunized population.

BACKGROUND: During August 2011-February 2012, an outbreak of type Π circulating vaccine-derived poliovirus (cVDPVs) occurred in Sichuan Province, China. METHODS: A field investigation of the outbreak was conducted to characterize outbreak isolates and to guide emergency response. Sequence analysis of poliovirus capsid protein VP1 was performed to determine the viral propagation, and a coverage survey was carried out for risk assessment. RESULTS: One clinical compatible polio case and three VDPV cases were determined in Ngawa County, Ngawa Tibetan and Qiang Autonomous Prefecture, Sichuan Province. Case patients were unimmunized children, 0.8-1 years old. Genetic sequencing showed that the isolates diverged from the VP1 region of the type Π Sabin strain by 5-12 nucleotides (nt) and shared the same 5 nt VP1 substitutions, which indicate single lineage of cVDPVs. Of the 7 acute flaccid paralysis cases (all>6 months) reported in Ngawa Prefecture in 2011, 4 (57.1%) cases (including 2 polio cases) did not receive oral attenuated poliovirus vaccine. Supplementary immunization activities (SIAs) were conducted in February-May, 2012, and the strain has not been isolated since. CONCLUSION: High coverage of routine immunization should be maintained among children until WPV transmission is globally eradicated. Risk assessments should be conducted regularly to pinpoint high risk areas or subpopulations, with SIAs developed if necessary.

[Analysis on mutation of S gene and P gene of hepatitis B virus in two counties of Sichuan Province].

OBJECTIVE: To analyze HBV S gene/P gene mutation in 2 counties (districts) of Sichuan province. METHODS: HBV DNA were extracted from sera positive both for HBsAg and HBeAg. After PCR and nucleotide sequencing, nucleotide/amino acid mutation in S and P gene were compared and analyzed. RESULTS: Of 47 serum samples from patients with chronic HBV infection, amino acid mutation in 'a' determinant occurred in 12 samples (25.53%,12/47), correlating with T126A, I126T/S, P127T, T131N, M133L, M133T and T140I; high proportion of mutation clustered in first loop of 'a' determinant (92.86%,13/14), rtV207I mutation in C domain of reverse transcription occured in one sample. CONCLUSION: Naturally occurring mutation in 'a' determinant clustered predominantly in the first loop and usually associated with altered antigenicity, posing a potential threat to successfully vaccinated individuals; Lamivudine-resistant mutant might occur in patient even without nucleotide analogue treatment.

[A seroepidemiologic analysis of hepatitis B in Sichuan province].

OBJECTIVE: To understand the changes of hepatitis B infection rates, before and after the hepatitis B vaccine was included into EPI, and to evaluate the effect of immunization which would lead to the development of a more appropriate hepatitis B control strategy. METHODS: Seroepidemiologic method, with multi-section random sampling method were chosen. 14 sites from 8 counties were involved. 2-4 ml of the vein blood was drawn from all the individuals engaged in the study including 3806 samples. HBsAg, anti-HBs, anti-HBc of the samples were tested with ELISA. RESULTS: Standardized positive rates of HBsAg and HBsAb were found as 7.05% and 29.77% respectively with the overall infection rate of HBV as 40.30%. The hepatitis B vaccine coverage of the children under 15 years was 70.73% and the positive rates for both HBsAg and anti-HBs were 2.62% and 56.68%, respectively. The coverage of hepatitis B vaccine among children under 3 years was 83.44% and the positive rates of both HBsAg and anti-HBs were 1.47% and 67.69% respectively, hepatitis B vaccine coverage of children under 3 years was 85.77%, with positive rates of HBsAg and anti-HBs as 1.78% and 75.44% respectively. CONCLUSION: Results from our study revealed that since the introduction of hepatitis B vaccination, the prevalence rates of HBsAg and HBV infection had an obvious decline, especially in children aged under 15 years of old, suggesting that some changes had occurred in the epidemic characteristics of hepatitis B in Sichuan.

[Laboratory confirmation of the first influenza A (H1N1) imported case in Mainland China].

The clinical throat swab specimen of an imported suspected case of influenza A (H1N1) was detec ted with real-time PCR, RT-PCR and subsequently confirmed by gene sequencing. The presence of influ enza A (H1N1) virus confirmed the first case with A (H1N1) infection in Mainland China.

Establishment of a nonradioactive assay for 2'-5' oligoadenylate synthetase and its application in chronic hepatitis C patients receiving interferon-alpha

AIM:To establish a nonradioactive assay for 2'-5' oligoadenylate synthetase (2-5 AS) and to measure the 2-5AS in peripheral blood mononuclear cell (PBMC) extracts of patients with chronic hepatitis C before IFN-alphainjection, 24 hours and one month after the first injection.METHODS: 2-5AS in cell extracts of PBMCs from 10 normal persons and 15 chronic hepatitis C patients were determined with PEI cellulose thin-layer chromatography.RESULTS: The assay of 2-5AS in human PBMC was found to be rapid, sensitive, specific and reliable. The 2-5AS activity of PBMC in normal persons was in a quite low level (2.0%), and it was increased about ten-folds after stimulation of IFN (19.7%), (P < 0.01). In 15 chronic hepatitic C patients, the basal levels of 2-5AS before IFN treatment were higher than those of normal persons, being much higher in the group showing poor response to IFN treatment, but 24h after the first injection of IFN-alphathe 2-5AS level showed a more rapid and much greater rise in those patients with a good response.CONCLUSION: 2-5AS may be a useful parameter of biological response during the IFN therapy.